Zion National Park is weighingwhether to have visitors make reservations to go hiking and picnic in the park—a first in the nationalparksystem.

Indeed, if Zion goes ahead with the measure, it could inspire similar decisions in other parks.

According to the Salt Lake Tribune, Zion officials are weighing an RSVP system following several years of increased visitations. Specifically, in addition to hiking and picnicking, officials are mulling whether to insist on reservations for visits to Zion’s main canyon. People without reservations would still be allowed to drive through the park—provided they pay the entrance fee. From the Tribune:

“We have to do something,” said park spokesman John Marciano. With limited budgets, Zion’s Park Service rangers routinely see long lines and plants trampled by visitors who also have cut some 30 miles of their own trails.

Zion isn’t the only U.S. national park with swelling numbers of tourists, and at least two national parks, in California and Hawaii, are testing more limited reservation systems for parking.

Overall, more than 330 million people visited U.S. national parks in 2016, a record. Visits were bolstered by the improving economy, cheap gas and marketing campaigns for the National Park Service’s 2016 centennial.

Zion is the fifth-most-visited park in the national park system. It’s particularly susceptible to overcrowding because many of its iconic cliffs and trails are located in the narrow, 6-mile-long (10-kilometer-long) Zion Canyon. The park already urges visitors to take a shuttle between March and November.

After a series of public meetings, Zion rangers are proposing an online reservation system, similar to the way campsites are reserved now. While certain hikes and activities require permits or reservations, the new system would apply to the entire main corridor of the park.

The number of reservations would be based on capacity, would vary by season, and could fall somewhere between a manageable 10,000 people a day and an overpowering 30,000 people a day, Marciano said.

One option would require a single reservation to enter and explore the park. A second would allow tourists to enter the park at a specific time and visit specific trails, like Angel’s Landing, a popular narrow cliff walk.

A third option would be to make no changes. But the park says that would allow continued degradation of the environment and the hours-long lines.

Public comment on the plan runs through Aug. 14. It could take at least two years before officials begin phasing in a reservation system.

Making reservations to visit a public park could be frustrating, especially if tourists who travel across the country or from abroad to see Zion’s spectacular vistas find themselves shut out if their plans change and they miss their time slot, said Darren Shipley, a video producer from Nashville, Tennessee, who’s visited Zion.

“I think there needs to be some flexibility,” Shipley said.

Administrators across the national park system are looking at ways to balance access with what (sometimes) amounts to “overvisitation.” Besides parks in California and Hawaii, places like Yellowstone, Grand Teton and Grand Canyon National Parks are mulling changes their car/shuttle policy, hoping more shuttles and less individual car traffic would curb congestion and parking woes.

Any change to the status quo is sure to come with its host of headaches, a fact acknowledged by Washington County director of tourism Roxie Sherwin, speaking to the Tribune, but visitation would (hopefully) accommodate a reservation system. Indeed, Sherwin notes many people already make reservations en route to Zion.

Administrators and tourism reps are also looking at ways to “spread the wealth” by promoting features in the vicinity of national parks like Zion and Yellowstone.